--- jsr166/src/test/tck/SystemTest.java	2003/08/31 19:24:55	1.1
+++ jsr166/src/test/tck/SystemTest.java	2017/05/14 03:09:25	1.14
@@ -1,71 +1,48 @@
 /*
- * Written by members of JCP JSR-166 Expert Group and released to the
- * public domain. Use, modify, and redistribute this code in any way
- * without acknowledgement. Other contributors include Andrew Wright,
- * Jeffrey Hayes, Pat Fischer, Mike Judd.
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ * Other contributors include Andrew Wright, Jeffrey Hayes,
+ * Pat Fisher, Mike Judd.
  */
 
-import junit.framework.*;
+import junit.framework.Test;
+import junit.framework.TestSuite;
 
-public class SystemTest extends TestCase {
+public class SystemTest extends JSR166TestCase {
     public static void main(String[] args) {
-	junit.textui.TestRunner.run(suite());	
+        main(suite(), args);
     }
-    
+
     public static Test suite() {
-	return new TestSuite(SystemTest.class);
+        return new TestSuite(SystemTest.class);
     }
 
-    public void testNanoTime1() {
-        // Nanos between readings of millis must be no longer than millis
+    /**
+     * Worst case rounding for millisecs; set for 60 cycle millis clock.
+     * This value might need to be changed on JVMs with coarser
+     * System.currentTimeMillis clocks.
+     */
+    static final long MILLIS_ROUND = 17;
+
+    /**
+     * Nanos between readings of millis is no longer than millis (plus
+     * possible rounding), and vice versa.
+     * This shows only that nano timing not (much) worse than milli.
+     */
+    public void testNanoTime() throws InterruptedException {
+        long m0 = System.currentTimeMillis();
+        long n0 = System.nanoTime();
+        Thread.sleep(1);
         long m1 = System.currentTimeMillis();
         long n1 = System.nanoTime();
-
-        // Ensure some computation that is not optimized away.
-        long sum = 0;
-        for (long i = 1; i < 10000; ++i)
-            sum += i;
-        assertTrue(sum != 0);
-
-        long n2 = System.nanoTime();
-
-        for (long i = 1; i < 10000; ++i)
-            sum -= i;
-        assertTrue(sum == 0);
-
-        long m2 = System.currentTimeMillis();
-        long millis = m2 - m1;
-        long nanos = n2 - n1;
-
-        assertTrue(nanos >= 0);
-        assertTrue(nanos <= millis * 1000000);
-    }
-
-    public void testNanoTime2() {
-        // Millis between readings of nanos must be no longer than nanos
-        long n1 = System.nanoTime();
-        long m1 = System.currentTimeMillis();
-
-        // Ensure some computation that is not optimized away.
-        long sum = 0;
-        for (long i = 1; i < 10000; ++i)
-            sum += i;
-        assertTrue(sum != 0);
-
+        Thread.sleep(50);       // avoid possibly scaled SHORT_DELAY_MS
         long m2 = System.currentTimeMillis();
-
-        for (long i = 1; i < 10000; ++i)
-            sum -= i;
-        assertTrue(sum == 0);
-
         long n2 = System.nanoTime();
-
-        long millis = m2 - m1;
-        long nanos = n2 - n1;
-
-        assertTrue(nanos >= 0);
-        assertTrue(millis * 1000000 <= nanos);
+        Thread.sleep(1);
+        long m3 = System.currentTimeMillis();
+        long n3 = System.nanoTime();
+        assertTrue((n2 - n1) / 1_000_000 <= m3 - m0 + MILLIS_ROUND);
+        assertTrue(m2 - m1 <= (n3 - n0) / 1_000_000 + MILLIS_ROUND);
     }
-
 }
-